roblesterjr04
Senior Member
I'm leaking gas from my carb, coming from the GAV needle. I replaced the needle, but still a problem. Anyone know if the needle housing is at fault or if I need a whole new lower bowl?
Leaking gas from choke/GAV needle
- Thread starter roblesterjr04
- Start date
Tom Endy
Well-known member
The GAV assembly threads are pipe threads, 1\8" pipe if I remember correctly. There needs to be a seal there to prevent leaking. Someone in the past may have run a straight tap through it and it has lost its ability to seal. I always put a small amount of pipe sealer on the threads. Don't use the white tape as pieces may migrate to the cap jet. Back the needle valve out a few turns before you tighten the base so the needle won't bottom out.
Tom Endy
Tom Endy
Marshall V. Daut
Well-known member
If it's a pre-January 1930 Zenith (or thereabouts), it should have a brass seat screwed into the lower casting for the GAV needle tip. It's much larger than the compensator jet, so you can't confuse the two. If that brass seat is missing, gas will pass by the needle and come out of the needle housing, as you describe. Is this an unknown carb to you, or has it been fine until now? Check to see that the brass seat is still screwed in place.
If, however, it's a later carb without the brass needle seat screwed in place, there is a seat ground into the lower casting from the factory where the needle tip beds against. If the hole is worn oversized or needle undersized, fuel could be flowing past the needle and out of the housing. Take a penlight and see if there are threads for a brass seat or whether the seat is part of the cast lower housing. Go from there to determine why the leak is occurring.
Marshall
If, however, it's a later carb without the brass needle seat screwed in place, there is a seat ground into the lower casting from the factory where the needle tip beds against. If the hole is worn oversized or needle undersized, fuel could be flowing past the needle and out of the housing. Take a penlight and see if there are threads for a brass seat or whether the seat is part of the cast lower housing. Go from there to determine why the leak is occurring.
Marshall
BILL WILLIAMSON
Well-known member
You are a FORTUNATE man, I can't recomember whut I did, 2 nights ago, let's see--------------------------------------------------
Bill W.
roblesterjr04
Senior Member
I probably should have led with this: its a Tilly.
Marshall V. Daut
Well-known member
"I probably should have led with this: its a Tilly. "
Yes, that would have been helpful. We generally assume unless otherwise stated by the poster that the part discussed is original to the Model A. The Tillotson is a popular carburetor found on many Model A's these days, but it is and always was an aftermarket item. I'm afraid what I and the others posted advised so far is probably not applicable to the Tillotson. Although the basic principles still apply, it is different internally from the Zenith and requires different troubleshooting and repair procedures. I gave up on warp-prone Tillotsons years ago, so perhaps someone conversant in Tillies can chime in here and help solve your problem.
Marshall
Yes, that would have been helpful. We generally assume unless otherwise stated by the poster that the part discussed is original to the Model A. The Tillotson is a popular carburetor found on many Model A's these days, but it is and always was an aftermarket item. I'm afraid what I and the others posted advised so far is probably not applicable to the Tillotson. Although the basic principles still apply, it is different internally from the Zenith and requires different troubleshooting and repair procedures. I gave up on warp-prone Tillotsons years ago, so perhaps someone conversant in Tillies can chime in here and help solve your problem.
Marshall
roblesterjr04
Senior Member
I suppose i'll start looking for a Z body to rebuild. Thanks for the info.